Detect missing the end of directives markers (---)

[fktn-k]

The current parser can't detect missing end-of-directives markers (---) between directives and contents like the following invalid YAML snippet:

%YAML 1.2
# The end-of-directives marker must be on this line.
foo: bar

So this PR has added detection of the lacking of those markers and several test cases to validate the added implementation.

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Pull Request Checklist

Read the CONTRIBUTING.md file for detailed information.

• Changes are described in the pull request or in a referenced issue.
• The test suite compiles and runs without any error.
• The code coverage on your branch is 100%.
• The documentation is updated if you added/changed a feature.

Please don't

• The C++11 support varies between different compilers and versions. Please note the list of supported compilers. Some compilers like GCC 4.7 (and earlier), Clang 3.3 (and earlier), or Microsoft Visual Studio 13.0 and earlier are known not to work due to missing or incomplete C++11 support. Please refrain from proposing changes that work around these compiler's limitations with #ifdefs or other means.
• Please refrain from proposing changes that would break YAML specifications. If you propose a conformant extension of YAML to be supported by the library, please motivate this extension.
• Please do not open pull requests that address multiple issues.

[github-actions]

Upload Coverage Event Notification

Coverage data has been uploaded for the commit 222f3c5392924b3dbc3e487b9e47fb1027ea495a.
You can download the artifact which contains the same file uploaded to the Coveralls and its HTML version.

Name	fkYAML_coverage.pr361.zip
ID	1604607502
URL	https://github.com/fktn-k/fkYAML/actions/runs/9527072485/artifacts/1604607502

[coveralls]

Pull Request Test Coverage Report for Build 9527072485

Details

• 8 of 8 (100.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 100.0%

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Totals
Change from base Build 9525662348:	0.0%
Covered Lines:	3896
Relevant Lines:	3896

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💛 - Coveralls